Semi-Automatic Rail Gun is a Laptop Killer

It’s huge, it’s unwieldy, and it takes 45 seconds to shoot all three rounds in its magazine. But it’s a legitimate semi-automatic railgun, and it’s pretty awesome.

Yes, it has its limits, but every new technology does, especially totally home-brew builds like this. The aptly named [NSA_listbot] has been putting a lot of work into his railgun, and this is but the most recent product of an iterative design cycle.

The principle is similar to other railguns we’ve featured before, which accelerate projectiles using rapidly pulsed electromagnets. The features list in the video below reads like a spec for a top-secret military project: field-augmented circular bore, 4.5kJ capacitor bank, and a custom Arduino Nano that’s hardened against the huge electromagnetic pulse (EMP) generated by the coils. But the interesting bits are in the mechanical design, which had to depart from standard firearms designs to handle the caseless 6 mm projectiles. The resulting receiver and magazines are entirely 3D printed. Although it packs a wallop, its cyclic rate of fire is painfully slow. We expect that’ll improve as battery and capacitor technology catches up, though.

Want to check out some more railgun builds? We’ve got them in spades — from one with $50,000 worth of caps to a wrist-mounted web-slinger.

Continue reading “Semi-Automatic Rail Gun is a Laptop Killer”

Pulsed Power and its Applications

Pulsed power is a technology that consists in accumulating energy over some period of time, then releasing it very quickly. Since power equals energy (or work) divided by time, the idea is to emit a constant amount of energy in as short a time as possible. It will only last for a fraction of a second though, but that instantaneous power has very interesting applications. With this technology, power levels of more than 300 terawatts have been obtained. Is this technology for unlimited budgets, or is this in reach of the common hacker?

Consider for example discharging a capacitor. A large 450 V, 3300 uF electrolytic capacitor discharges in about 0.1 seconds (varies a lot depending on capacitor design). Since the energy stored in it is given by 1/2 CV², which gives 334 Joules of energy, the power delivered will be 3340 watts. In fact a popular hacker project is to build large capacitor banks. Once you have the bank, and a way to charge it, you can use it to power very interesting devices such as:

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A portable, 1.25 kJ coilgun by [Jason Murray]

Railguns in particular are subject to serious research. You may have read about the navy railgun, capable of reaching a muzzle speed of more than 4,600 mph (around Mach 6), more than any other explosive-powered gun. Power is provided by a 9-megajoule capacitor bank. The capacitors discharge on two conducting rails, generating an electromagnetic field that fires the projectile along the rails. The rail wear due to the tremendous pressures and currents, in the millions of amperes range, is still a problem to be solved.

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24kJ Capacitor Bank

The Leyden jar capacitor posted the other day fails to compare to what [FastMHz], one of the members over at the 4HV.org forums, has been busy building, a 24kj capacitor discharge bank. This capacitor bank will be configured for 4500v @ 2400uF and can be charged up slowly using microwave oven transformers. It can then release all its stored energy in under a millisecond through a triggered spark gap. This allows for some pretty big sparks as seen in this video, we are not sure about the laughing in the video maybe the power has gone to his head? Continue reading “24kJ Capacitor Bank”